A coauthor of a disputed study on a new way generating stem cells through exposure to acid and other stresses has asked for its retraction, it was reported Monday.

Teruhiko Wakayama asked for retraction of two papers describing so-called STAP cells, according to the Yomiuri Shimbun. The papers had been published in the Jan. 30 edition of the journal Nature. Other news outlets, including the Wall Street Journal and the Boston Globe, quickly followed up with the call for retraction.

The original announcement gained worldwide attention because it promised an easy way to generate pluripotent stem cells, which act like embryonic stem cells. Simply immersing cells in an acid bath or squeezing them was enough to reprogram them to the embryonic-like state, the scientists reported. The acronym STAP stands for stimulus-triggered acquisition of pluripotency.

However, researchers attempting to replicate the experiment, including those at the Salk Institute and The Scripps Research Institute in La Jolla, have so far reported failure. And errors in the papers, including duplication of images, have caused scientists to question the findings.

The first author of both papers is Haruko Obokata, 30, of the Riken Center for Developmental Biology in Japan. She was hailed as a scientific prodigy after the research was published. Another coauthor, Charles Vacanti, chairman of the Anesthesiology department at Brigham and Women’s Hospital in Boston, had previously said the errors were caused by overwork and didn't affect the results.

But on Monday, Wakayama said the irregularities render the findings questionable.

"Wakayama said images that show pluripotency of STAP cells look almost identical to those used in Obokata’s doctoral thesis about pluripotent stem cells that exist in human body," the Yomiuri Shimbun reported.

Wakayama is probably acting out of a sense of duty, said Jeanne Loring, a stem cell scientist at The Scripps Research Institute.

"I don't know him well, but I have known him a long time," Loring said. "He's the real thing. He's a very honorable person. He was the one who cloned the first mouse, which was called Cumulina, and I actually got to meet her."

Loring said the incident makes her sad, because the stem cell field has had to deal with retracted studies and outright fraud that has placed a cloud over stem cell research.

Even before the announcement, Loring said she had lost interest in the STAP cells because even if the phenomenon was real, it was impractical. Loring is sticking with induced pluripotent stem cells, made from skin cells. The IPS cells were first produced in animals in 2006 and from people the next year. Loring and colleagues are investigating whether IPS cells made from Parkinson's patients can be used as therapy, to replace brain cells destroyed by the disabling disease.